Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$114.80	9.398%	$125.5889	$125.59	$125.60	$125.60
Purchase #2	$238.57	8.481%	$258.8031	$258.80	$258.80	$258.80
Purchase #3	$172.63	7.527%	$185.6239	$185.62	$185.60	$185.60
Purchase #4	$31.98	4.149%	$33.3069	$33.31	$33.30	$33.30
Purchase #5	$17.79	8.302%	$19.2669	$19.27	$19.25	$19.30
Purchase #6	$83.44	7.299%	$89.5303	$89.53	$89.55	$89.50
Purchase #7	$29.61	10.103%	$32.6015	$32.60	$32.60	$32.60
7 purchase totals =	$688.82		$744.7215	$744.72	$744.70	$744.70